Audio Pro Loudspeaker Repairs

Audio Pro B2-40 Active Loudspeakers

Audio Pro B2-40 Active Loudspeaker Audio Pro B2-40 Active Loudspeaker

This worked but the auto off switch didn't auto switch off! I had to get my scope out for this (a rare occurrence). There was noise in the output of the opamp TL082 which is in the auto sense section. This was just enough to keep the voltage up to the next opamp instead of letting it decay slowly thereby turning the relay off. As I type this I don't have the inclination to find the faulty component (its either the opamp itself, the zener across the feedback resistor or one of the high value resistors) put a 33n capacitor across the 100k f\b resistor to reduce the noise level sufficiently to allow the voltage to decay - happy days.

Audio Pro A4-14 Active Loudspeakers

Audio Pro A4-14 Active Loudspeaker Audio Pro A4-14 Active Loudspeaker

These didn't do anything, checking the amp I found the output transistors were short circuit replaced them and the speakers worked but the sound was not quite right. The surrounds needed replacing. A common problem is the tantalum capacitor in the middle of the power amp board becomes a resistor and stops the amp from working as it should, the large supply capacitors were replaced as they had leaked.